Building Tightness Limits

Otherwise known as the BTL...hold the mayo.

The building tightness limits (BTL) show how tight, well, the building is. When a weatherization contractor air seals a home and runs a blower door, there is a number that is very important that when you exceed it - additional steps must be taken.

Each home has a different limit based upon size of the home, number of occupants, pets, weather they smoke (occupants, no pets) and other moisture sources. When a home gets too tight, the indoor air quality takes a turn for the worse. Imagine if you will being in a room that has a window that's open all the way. Then imagine if you will 3 people in the room, one of the people smoke, there's a dog and an aquarium. Now, one last time, imagine if the window is shut so that only 1" remains open. Is the indoor air quality better or worse?

Duh, it's worse. What could be done (besides opening the window back up)? Introduce an exhaust fan. This aids in the recycling of the air.

The key to exhaust fans shall come in a later writing. It's time for HZG to go to "get thrown" training.